Classic tiramisu

Method

1. Separate the eggs, setting the whites aside. Put the yolks in a large mixing bowl with the sugar and whisk with an electric mixer until pale and thick – the mixture should leave a trail when the beaters are lifted. Whisk in the mascarpone, marsala and vanilla until well combined (the mixture will be quite runny).
2. Whisk the egg whites in a clean bowl with clean beaters until stiff. Gently fold the whites into the mascarpone mixture with a balloon whisk or metal spoon, adding just 1 tbsp at first to loosen, then adding the rest in 2 batches. Chill for 25 minutes.
3. Stir the Kahlúa into the espresso in a shallow bowl. Soak one side of the savoiardi biscuits in the mixture for a couple of seconds before turning them over and repeating (they should be moist but not falling apart; see Know-how).
4. Arrange half the soaked savoiardi biscuits in a single layer in the base of a large rectangular dish, or divide among 8-10 individual dishes. Top with half the mascarpone mixture, followed by half the chopped chocolate. Repeat with the remaining biscuits, mascarpone mix and chocolate. Cover the tiramisu(s) with cling film and chill for at least 8 hours, preferably overnight.
5. Take out of the fridge around 20 minutes before you want to eat it. Dust with cocoa powder, sprinkle with more chopped chocolate, then serve.